Zirconium metal has historically been a material of construction, in particular cladding for fuel rods, for nuclear reactors, and there has been a continuing interest in reducing its tendency to adsorb thermal neutrons. The more transparent the internal materials of construction of a nuclear reactor are to such thermal neutrons the more efficiently the reactor will function since a certain number of these neutrons are necessary to sustain the nuclear reaction and their production must compensate for the adsorption by the internal materials of construction. Early efforts were directed to separating zirconium from hafnium. The two elements occur together naturally but the hafnium has a substantially larger capture section for thermal neutrons. Such efforts involved both chromatographic techniques using an ion exchange resin and various solvent extraction techniques.
More recent efforts have been directed to isolating a zirconium isotope with either a particularly high or a particularly low cross section to thermal neutrons. This allows the production of a zirconium with a lower average cross section than one composed of the naturally occurring isotope distribution. These efforts at isotope separation have generally involved some type of solvent extraction. These separation techniques are generally only able to separate one isotope at a time. Thus they do not provide a means for simultaneously isolating the zirconium 90 and 94 isotopes which are recognized as having particularly small cross sections (one source lists them as 0.055 and 0.031 Barns, respectively, as compared to 0.567 Barns for zirconium 91 and 0.1430 for zirconium 92).
It is an object of the present invention to provide a process for simultaneously isolating both zirconium 90 and zirconium 94, which are the isotopes which both are fairly abundant and have low thermal neutron capture cross sections. It is a further object of the present invention to provide a more efficient process than solvent extraction by utilizing a chromatographic technique. It is yet another object of the present invention to provide a continuous technique for separating the isotopes of zirconium utilizing a continuously operating chromatographic technique.